CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income	$ 292,888	$ 313,916	$ 282,179	$ 266,049	$ 64,812	$ 166,531	$ 175,991	$ 186,185	$ 1,155,032	$ 593,519	$ 743,499
Other comprehensive income (loss), net of tax
Unrealized gains (losses) on derivatives, net of tax of $1,694, $19,006 and $5,452 respectively									(5,673)	(21,408)	(30,300)
Realized (gains) losses on derivatives recognized in net income, net of tax of $(11,013), $(26,899) and $230, respectively									36,870	63,687	(6,977)
Change in pension and postretirement benefit plan liability, net of tax of $(1,425), $(878) and $11,128, respectively									4,771	(4,175)	(16,693)
Other comprehensive income (loss) on investments in unconsolidated affiliates, net of tax of $(724), $145 and $270, respectively									2,424	(970)	(1,505)
Total other comprehensive income (loss), net of tax									38,392	37,134	(55,475)
Comprehensive income									1,193,424	630,653	688,024
Less: Comprehensive income attributable to noncontrolling interests									3,329	236,704	363,093
Comprehensive income attributable to ONEOK									$ 1,190,095	$ 393,949	$ 324,931